title: 17O solid-state NMR as a sensitive probe of hydrogen bonding in crystalline and amorphous solid forms of diflunisal.
abstract: (17)O solid-state NMR (SSNMR) can provide insight into hydrogen bonding interactions in pharmaceutical polymorphs, cocrystals, and amorphous dispersions. When combined with straightforward (17)O synthetic labeling, the use of (17)O SSNMR allows for direct study of key interactions such as hydrogen bonding in these systems. In this work, novel applications of (17)O SSNMR are demonstrated in the analysis of a polymorph of diflunisal, a cocrystal of diflunisal with pyrazinamide, and amorphous dispersions of diflunisal in two polymers. The observation of the (17)O nucleus is shown to be a highly specific and useful alternative to more conventional studies of the (1)H, (13)C, and (19)F nuclei in these systems and offers unique insight into hydrogen bonding interactions. Quantum chemical calculations are used to assess the (17)O SSNMR measurements for the polymorph of diflunisal for which a crystal structure has been previously determined. Empirical hydrogen bonding trends are then examined in the cocrystal and amorphous solid forms using (17)O NMR parameters. A novel application of (1)H-(17)O cross-polarization heteronuclear correlation (CP-HETCOR) experiments is also demonstrated for the cocrystal and two dispersions. This experiment offers specific information about proton environments in proximity to the labeled oxygen sites. The use of (17)O SSNMR techniques extends the utility of SSNMR in applications to cocrystals and amorphous dispersions.
authors.affiliation: Product Development, GlaxoSmithKline plc , 709 Swedeland Rd., King of Prussia, Pennsylvania 19406, United States.
authors.forename: Frederick G
authors.initials: FG
authors.lastname: Vogt
authors.forename: Hao
authors.initials: H
authors.lastname: Yin
authors.forename: Rachel G
authors.initials: RG
authors.lastname: Forcino
authors.forename: Lianming
authors.initials: L
authors.lastname: Wu
mesh_terms: D004061:Diflunisal / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010103:Oxygen Isotopes / Q000737:chemistry
chemical_list: D010103:Oxygen Isotopes; D004061:Diflunisal